“超级细菌”MRSA的克星来了 存在南极海绵动物中

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近日，研究者在一种南极海绵动物中发现了一种物质，该物质可以有效杀灭98%的耐药超级菌——耐甲氧西林金黄色葡萄球菌（methicillin-resistant?Staphylococcus aureus，MRSA），目前该菌在美国快速传播。
随着越来越多的细菌对目前使用的抗生素产生耐药性，科学家正在极力地寻找可以抵御这些病菌的物质，这项研究发现的存在于南极海绵中的一种物质可能是其中的一个选择。
金黄色葡萄球菌感染是很常见的感染，特别是在医院环境中。在正常情况下，这种病菌不是个难治的对象。但是MRSA是一株发展为对目前大部分抗生素耐药的菌株，也就说，这种病菌可以从皮表感染迅速蔓延，从而危及生命。
根据美国疾病控制与预防中心（CDC）的估计，美国每年有80000人被诊断为MRSA感染，大约有11000人死于MRSA并发症。目前，医生根本没有很多的方法可以有效治疗这种感染。
因此，这种物质的发现让研究者很振奋，这种物质被命名为“darwinolide”，存在于一种名为Dendrilla membranosa南极海绵动物中。目前在实验室的数据显示，darwinolide可杀灭98.4%的MRSA。
研究者已经对这种物质申请了专利，不过仍然在研究这种物质发挥作用的机制。最新的研究结果显示，这种物质有一种非常特别的结构，使得这种物质很容易渗透到MRSA细胞内，从而发挥杀菌作用。
下一步，研究者希望能在实验室合成darwinolide，这样就不用从南极海绵中提取darwinolide。接下来研究者打算在临床试验中测试这种物质的灭菌效果，如果有效，那么darwinolide可以拯救成千上万的患者生命。
来源：药渡

Natural product darwinolide may help combat fatal MRSA infection

A serious and sometimes fatal bacterial infection, known as methicillin-resistant Staphylococcus aureus (MRSA), may soon be beatable thanks to the efforts of University of South Florida scientists who have isolated and tested an extract from a sponge found in Antarctica. The sponge extract, known as Dendrilla membranosa, yields a new, natural product chemical which has shown in laboratory tests that it can eliminate more than 98 percent of MRSA cells. The research team has named the new chemical "darwinolide."

The study describing their methods and results was published this week in the American Chemical Society's journal Organic Letters.

While years ago the highly-resistant MRSA infection was particularly problematic in places such as hospitals and nursing homes, it has developed into an infection that can be found in commonly-used places such as gyms, locker rooms and schools.

"In recent years, MRSA has become resistant to vancomycin and threatens to take away our most valuable treatment option against staph infections," said study co-author and USF microbiologist Dr. Lindsey N. Shaw.

MRSA is unique in that it can cause infections in almost every niche of the human host, from skin infections, to pneumonia, to endocarditis, a serious infection of tissues lining the heart. Unfortunately, the pace of the pharmaceutical industry's efforts to find new antibiotics to replace those no longer effective has slowed in recent years, said Shaw.

Like many other bacterium, the MRSA bacteria forms a biofilm.

"Biofilms, formed by many pathogenic bacteria during infection, are a collection of cells coated in a variety of carbohydrates, proteins and DNA," said Shaw. "Up to 80 percent of all infections are caused by biofilms and are resistant to therapy. We desperately need new anti-biofilm agents to treat drug resistant bacterial infections like MRSA."

USF chemistry professor Dr. Bill Baker and colleagues have literally gone to the 'ends of the Earth' to help in the fight against MRSA. Baker, who also serves as director of the USF Center for Drug Discovery and Innovation (CDDI), studies the chemical ecology of Antarctica and dives in the frigid waters near Palmer Station to retrieve marine invertebrates, such as sponges, to carry out "natural product isolation," which means drawing out, modifying and testing natural substances that may have pharmaceutical potential.

His group led the effort to extract and characterize chemical structures to create darwinolide from the freeze-dried Antarctic sponges and then test in Shaw's lab to determine its effectiveness against the MRSA bacteria.

"When we screened darwinolide against MRSA we found that only 1.6 percent of the bacterium survived and grew. This suggests that darwinolide may be a good foundation for an urgently needed antibiotic effective against biofilms," said Baker, whose research team "rearranged" the chemical composition of the extracted sponge.

In the last 70 years, despite the discovery and use of antibiotics to treat infections, bacterial disease remains the second-leading cause of death globally, especially among children and the elderly, noted the researchers. In the U.S. alone there are two million hospital acquired infections annually with at least 100,000 deaths, many resulting from bacteria resistant to current antibiotics.


"We suggest that darwinolide may present a highly suitable scaffold for the development of urgently needed, novel, anti-biofilm-specific antibiotics," concluded the researchers.